Underground storage in permeable formations



Oct. 13, 1964 J. w. MARX 3,152,640

UNDERGROUND STORAGE IN PERMEABLE FORMATIONS Filed Feb. 26, 1962 3 Sheets-Sheet l INVENTOR. J W. MARX F I 6. 4 ATTORNEYS Oct. 13, 1964 J. w. MARX UNDERGROUND STORAGE IN PERMEABLE FORMATIONS 5 Sheets-Sheet 2 Filed Feb. 26, 1962 INVENTOR. J. W. MARX BY f A T TORNEYS Oct. 13, 1964 J. w. MARX 3,152,640

UNDERGROUND STORAGE IN PERMEABLE FORMATIONS Filed Feb. 26, 1962 3 Sheets-Sheet 3 INVENTOR. J. W. MARX United States Patent ()fiflce 3,152,646 Patented Oct. 13, 1964;

3,152,640 UNEBER-GRUUND STQRAGE IN PERMEABLE FGRMATIQNS John W. Marx, liartlesville, Okla, assignor to Phillips Petroleum Company, a corporation of Delaware Filed Feb. 2-5, 1%2, Ser. No. 175,608 3 tilt-aims. (til. 166-9) This invention relates to the underground storage of fluids. In one aspect, the invention relates to a method of confining fluids stored in an underground porous formation through the use of a confining fluid. In another aspect, the invention relates to an underground storage reservoir comprising means for confining the stored fluid with a confining fluid.

In recent years much attention has been directed to the underground storage of fluids, especially to the storage of hydrocarbon fuels, gaseous, liquid or liquefied normally gaseous. In addition to underground storage containers formed by mining operations in impervious formations, the dissolution of soluble material such as rock salt through the use of a solvent such as water, the use of buried, preformed vessels, etc., naturally existing permeable formations also have been utilized. Many large strategically located underground reservoirs from which liquid petroleum and gas have been recovered can be used where storage in very large quanities is desired. In many of these reservoirs structural closure or a naturally existing water drive define a reservoir, but these reservoirs often are so large as to be impractical for the storage and recovery of hydrocarbon fuels in quantities desired by present commercial interests. Therefore, some means for providing reservoirs small enough to be of commercial use within existing porous formations is desirable.

An object of my invention is to store and recover fluids from porous underground formations.

Another object of my invention is to provide fluid storage reservoirs of desirable size in formations where structural closure or natural water drive define reservoirs too large to be of economical use.

Another object of my invention is to provide fluid storage reservoirs within porous underground formations where structural closure and a naturally existing confining water drive are absent.

According to my invention fluid is stored in a porous underground formation by injecting the fluid into a centrally located well communicating with the formation, injecting a confining fluid into alternate wells of a line of wells defining a boundary of the desired reservoir area and withdrawing a portion of the confining liquid from the remaining wells of this line. The injection and withdrawal rates are adjusted to maintain a pressure of the confining fluid suflicient to confine the stored fluid, and where the stored product is a liquefied normally gaseous product suflicient to maintain the stored product in the liquid state.

Further according to my invention, there is provided an underground storage reservoir including a centrally located well communicating with a porous underground formation, through which a fluid to be stored can be introduced and Withdrawn, a line of wells along desired boundary of the reservoir, means to inject a confining fluid in alternate wells of the line and means to withdraw a portion of the confining fluid from the remaining wells of the line.

The line of wells can be a line completely encircling the desired reservoir area, thereby defining the complete boundary of the storage area, or can be a line defining only a portion of the boundary, the remainder of the boundary being formed by structural closure or other means. The inflow and outflow of the confining fluid is regulated to maintain a pressure within the formation slightly greater than that exerted by the stored fluid in the same area. Where desirable or necessary, the pres sure of the storage reservoir can be regulated to maintain a normally gaseous fluid in a liquid state, or to provide suflicient pressure for withdrawal of the stored fluid without pumping.

In the drawing FIGURE 1 is a contour taken at the upper surface of a typical storage reservoir area utilizing a line of wells partially defining the reservoir boundary.

FIGURE 2 is a cross section taken along the line 22 of FIGURE 1.

FIGURE 3 is a contour taken on the top of a formation in which the reservoir is formed by a line of Wells completely surrounding the storage area.

FEGURE 4 is a cross section taken along the line 44 of FIGURE 3.

FTGURE 5 illustrates fingering which can occur where a confining fluid is injected into a line of wells along a desired boundary of an underground storage reservoir.

FlGURE 6 illustrates a similar situation, the improvement when, the confining fluid is withdrawn from alternate wells.

FIGURE 7 is a vertical cross section of a typical reservoir formed in a porous underground formation illustrating a stored fluid injection and withdrawal well and typical confining fluid injection and withdrawal wells.

In FIGURE 1 a reservoir is formed in a porous underground formation 11 by natural closure and an underlying aquifer along approximately three-fourths of the periphery of the reservoir. This can be seen in the cross section in FIGURE 2 where the aquifer 12 cooperates with roof 13 formed by an impermeable formation overlying the porous formation 11. It is seen, however, that the roof of the porous formation 11 does not provide suflicient closure on the other boundary to permit storage of the desired fluid within a small enough reservoir to be practical. Therefore, a line of wells is provided to define the reservoir boundary along this side. This line of wells comprises alternate input wells 14 and output wells 16. The stored fluid is introduced and withdrawn through a centrally located well 17. The boundary of the reservoir is indicated by dotted line 13.

FIGURES 3 and 4 illustrate a reservoir formed in a relatively flat section of permeable formation by a line of wells completely surrounding the desired reservoir area.

Alternate input wells 19 and output wells 21 are provided and the confining fluid introduced into and circulated between these wells defines the complete boundary of the desired reservoir.

It has been proposed to drill a ring of wells at optimum spacing around the periphery of a proposed reservoir and to pump water into the wells until a confining ring of water has been established. However, such operation is impractical because of excessive loss of hydrocarbon materials through channels established between the wells. FIGURE 5 illustrates the situation which exists when an attempt is made to confine a stored fluid by injecting a confining fluid along a desired boundary. In this figure confining fluid injection wells are represented at 22 and a stored fluid injection and withdrawal well at 23. The shaded area illustrates typical paths of the confining fluid, the direction of flow being indicated by the solid lines while the movement of the stored fluid is indicated by the dashed lines. Here it can be seen that, even though the pressure of the confining fluid at the point where it is introduced into the formation is greater than the pressure of the stored fluid at that distance from the well 23, due to the path of flow which occurs in finger-like configurations, paths remain through which the stored fluid can escape to the area outside the ring of confining fluid Wells and thus be lost.

In accordance with my invention a ring of wells is drilled about the periphery of the reservoir but alternate wells are operated as input or output wells, respectively. That is, the first Well in the ring is operated as a water input well and the two adjacent wells are operated as output wells. This pattern is continued around the ring. Operating in this manner, as fingers develop when the confining liquid is forced into the reservoir, they are caused to coalesce by channels set up in the opposite direction toward the intermediate water-producing wells. FIGURE 6 illustrates the condition which exists when a portion of the confining fluid is Withdrawn through wells altermated with the confining fluid injection wells. Here injection wells 26 are interspersed with confining fluid withdrawal wells 27. Although fingering still takes place within the porous formation, a continuous path is provided from the confining fluid injection wells 26 to the confining fluid withdrawal Wells 27. Since the pressure in the confining fluid is maintained slightly greater than that which can occur in the stored fluid at this position, the stored fluid cannot escape from the reservoir. Although some mixing or absorption of the stored fluid can occur at the boundary of the confining fluid, this stored fluid cannot escape from the reservoir, but if it approaches a confining fluid withdrawal well 27, is withdrawn with the confining fluid which it can be separated from and recycled into the reservoir.

FIGURE 7 illustrates a cross section of a reservoir similar to that illustrated in FIGURE 4 but enlarged to permit the illustration of more details. This illustration is, however, schematic and not to scale, the relative dimensions between length and diameter of wells, the distance between wells, etc., not permitting exact scale drawings. In this view a centrally located stored fluid input and withdrawal well 31, a confining fluid injection well 32 and a confining fluid withdrawal well 33 penetrate an underground porous formation 34. Each of these wells is completed in a conventional manner, for example, with a casing string extending to the surface of the formation, a central tubing provided with a packer near the lower end of the casing, casing and tubing heads and a control valve on the tubing as illustrated. Of course, other types of well completion can be utilized, as for example a casing string cemented through the formation and perforated at desired intervals, etc. As will be understood by reference to FIGURE 3, the confining fluid injection and withdrawal wells are spaced alternately around the reservoir area so that the wells illustrated, wells 32 and 33, normally do not cooperate directly with each other in the injection and withdrawal of the confining fluid, but directly with adjacent wells.

In this particular embodiment, water, from a source not shown, is injected by a pump 36 through valve 37, and well tubing 38 into the well bore 39 from which it is permitted to enter formation 34. A liquefied petroleum gas product from tank 41 is injected by pump 42 through valve 43 and tubing 44 into well bore 46 from which it enters the formation 34 at a generally centrally located position with reference to the defined reservoir area. Well 31 also is provided with a bottom hole pump 47 which can be, for example, an electrically driven centrifugal pump supplied with power from a generator 48, driven by prime mover (not shown) and conductors 49. In the description of well 31 it has been assumed that pump 47 is of a type through which fluid can be forced into formation 34 as well as being used for withdrawal of the fluid at the desired time. However, it is preferred that an additional path for injected fluid be provided as, for example, by providing a second tubing, by providing a check .53. valve in the packer (or eliminating the packer), providing a pressure opening valve in the lower portion of the tubing, below the packer but above the pump, or by other means. Where pressure exerted by the confining fluid is relied upon for removal of the stored fluid, pump 47 can be dispensed with.

Well 33 is provided with a similar down-hole pump 51 by means of which the confining fluid, in this instance water, is withdrawn through tubing 52 and valve 53. Power for pump 51 is provided by generator 56 through conductors 57. Usually it is desirable that provision be made to reinject the water withdrawn through well 33 into a confining fluid injection well, such as well 32, although normally the water is reinjected through an adjacent well.

Where desirable, separating means 53 are provided for separating any stored fluid which is withdrawn with the confining fluid, the stored fluid outlet being indicated at 59 and the confining fluid (water) outlet being indicated at 61.

Reasonable variation and modification are possible within the scope of my invention which sets forth a method for storing a fluid in a porous underground formation comprising providing a boundary for the reservoir by injecting a confining fluid into alternate wells of a line of wells defining a boundary, and withdrawing confining fluid from the remaining wells, and an underground storage reservoir comprising a line of wells defining a boundary of the reservoir by means of confining fluid injected through alternate wells and withdrawn through the remaining wells of the line.

I claim:

1. A method for storing fluid in a porous underground formation comprising the steps of:

injecting a fluid to be stored into a central well communicating with said formation;

injecting a confining fluid into alternate wells of a line of Wells defining a boundary of a desired reservoir area in said formation; and

producing a portion of said confining liquid from the 49 remaining wells of said line of wells.

2. A method for storing fluid in a porous underground formation comprising the steps of:

injecting a fluid to be stored into a central well communicating with said formation;

injecting a confining fluid into alternate wells of a line of wells surrounding said central well thereby defining the periphery of a desired reservoir area in said formation; and

producing a portion of said confining liquid from the remaining wells of said line of wells.

3. A method for storing a fluid in a porous underground formation comprising the steps of injecting a fluid to be stored into a central well communicating with said formation;

injecting a confining fluid into alternate wells of a line of wells defining a boundary of a desired reservoir area in said formation;

Withdrawing a portion of said confining liquid from the remaining wells of said line of wells; and

60 regulating the inflow and outflow of said confining fluid to maintain sufltcient pressure in said reservoir area to maintain said fluid to be stored in the liquid state.

References Cited in the file of this patent 5 6 UNITED STATES PATENTS 

1. A METHOD FOR STORING FLUID IN A POROUS UNDERGROUND FORMATION COMPRISING THE STEPS OF: INJECTING A FLUID TO BE STORED INTO A CENTRAL WELL COMMUNICATING WITH SAID FORMATION; INJECTING A CONFINING FLUID INTO ALTERNATE WELLS OF A LINE OF WELLS DEFINING A BOUNDARY OF A DESIRED RESERVOIR AREA IN SAID FORMATION; AND PRODUCING A PORTION OF SAID CONFINING LIQUID FROM THE REMAINING WELLS OF SAID LINE OF WELLS. 